#include <iostream>
#include <stdio.h>

using namespace std;

int main() {
    unsigned long long a;
    unsigned long long b;
    unsigned long long c;
    cin >> a >> b;
    int d = b-a;
    a = 1;
    b = 1;
    c = 1;
    for(int i = 2; i <= d; i++){
        c = a+b;
        a = b;
        b = c;
    }
    cout << c;
    return 0;
}